Improving Broadband White‐Light Emission Performances of 2D Perovskites by Subtly Regulating Organic Cations

Abstract

Recently, 2D organic–inorganic hybrid lead halide perovskites have attracted intensive attention in solid‐state luminescence fields such as single‐component white‐light emitters, and rational optimization of the photoluminescence (PL) performance through accurate structural‐design strategies is still significant. Herein, by carefully choosing homologous aliphatic amines as templates, isotypical perovskites [DMEDA]PbCl4 (1, DMEDA=N,N‐dimethylethylenediamine) and [DMPDA]PbCl4 (2, DMPDA=N,N‐dimethyl‐1,3‐diaminopropane) having tunable and stable broadband bluish white emission properties were rationally designed. The subtle regulation of organic cations leads to a higher degree of distortion of the 2D [PbCl4]2− layers and enhanced photoluminescence quantum efficiencies (<1 % for 1 and 4.9 % for 2). The broadband light emissions could be ascribed to self‐trapped excitons on the basis of structural characterization, time‐resolved PL, temperature‐dependent PL emission, and theoretical calculations. This work gives a new guidance to rationally optimize the PL properties of low‐dimensional halide perovskites and affords a platform to probe the structure–property relationship.

Systematic Approach of One-Dimensional Lead Perovskites with Face-Sharing Connectivity to Realize Efficient and Tunable Broadband Light Emission

“…21,33,51 The PLQY of 5.17% for the whitelight emission is comparable to the vast majority of hybrid white-light-emitting perovskite materials, such as (EDBE)-PbBr 4 (9%), (2meptH 2 )PbBr 4 (3.37%), (EDBE)PbCl 4 (2%), (N-MEDA)PbBr 4 (1.5%), (C 4 H 9 NH 3 ) 2 PbCl 4 (1%), and so forth (Figure S5b and Table S2). 21,33,51,56,57 Time-resolved PL spectrum monitoring emission at 550 nm gives an average PL lifetime of 68.13 ns, which is also longer than most of hybrid perovskites with STE broadband light emissions (Figure 4f). In addition, the PL decay curve gives a short lifetime of 2.25 ns for emission at 470 nm (Figure S6).…”

“…The PL excitation spectrum of compound 1 covers a broad range of 230−375 nm with two higher peaks at about 280 and 336 nm, which are close to the intensive excitonic absorption bands (Figure S4). As shown in Figure 4, upon the excitation of 280 nm UV light, compound 1 displays a Gaussian-shaped broadband emission spectrum with the highest peak at about 16,22,56,57 Hence, it is reasonable to attribute this Gaussian-shaped broadband yellow light emission to radiative recombination of self-trapped excited state with single energy minimum.…”

Organic‐Inorganic Hybrid Low‐dimensional Lead Iodides with Broadband Yellow to Red Light Emissions

“…By using organic cations to replace Cs + , a large amount of organic-inorganic hybrid lead halide perovskites have been explored extensively as luminescent materials. [11][12][13] For example, α-(DMEN)PbBr 4 (2D, DMEN = 2-(dimethylamino)ethylamine), (2MeptH 2 )PbCl 4 (2D, 2Mept = 2-methyl-1,5-diaminopentane), C 5 H 14 N 2 PbCl 4 (1D), C 4 N 2 H 14 PbBr 4 (1D), display broadband whitelight emissions with potential application value in solid state lighting device. [14][15][16][17] It is well known that low-dimensional hybrid lead halides readily exhibit broadband white-light emissions with high color rendering indices and PLQYs mainly deriving from the strong electron-phonon coupling effect in soft and distorted crystal lattice.…”

“…At the same time, 3D perovskites can be tailored into manifold 2D layers, 1D chains and 0D clusters containing various connecting manners of corner‐, edge‐ and face‐sharing between octahedral [PbX 6 ] units. By using organic cations to replace Cs + , a large amount of organic‐inorganic hybrid lead halide perovskites have been explored extensively as luminescent materials [11–13] . For example, α ‐(DMEN)PbBr 4 (2D, DMEN=2‐(dimethylamino)ethylamine), (2MeptH 2 )PbCl 4 (2D, 2Mept=2‐methyl‐1,5‐diaminopentane), C 5 H 14 N 2 PbCl 4 (1D), C 4 N 2 H 14 PbBr 4 (1D), display broadband white‐light emissions with potential application value in solid state lighting device [14–17] …”

Metal Halide Scaffolded Assemblies of Organic Molecules with Enhanced Emission and Room Temperature Phosphorescence

“…Organic metal halide hybrids consisting of organic cations and metal halide anions have received significant attention due to their structure diversity, unique photophysical properties, and wide range of applications. − Single crystals with different dimensionalities at the molecular level have been developed by carefully choosing the organic cations and metal halides, as well as controlling the synthetic conditions. − In most of these hybrid materials developed to date, organic cations with wide-bandgap are used to template the assemblies of metal halides without contributing directly to their photophysical properties. − Recently, photoactive organic cations have been used to develop organic metal halide hybrids with emissions from both organic cations and metal halides, or solely from organic cations. − The cocrystallization of organic cations with metal halides could enable the manipulation of their photophysical properties by affecting their packing modes and intermolecular interactions. For instance, protonated enrofloxacin exhibited higher PLQE and smaller Stokes shift when it was cocrystallized with SnCl 6 2– , as compared with other metal halides (Pb 2 Cl 6 2– to Bi 2 Cl 10 4– ), due to stronger inter- and intramolecular interactions .…”